Bacterial endotoxic lipopolysaccharides (LPS) can initiate fever, profound hypotension (shock), disseminated intravascular coagulation, multisystem organ failure and death. There is substantial evidence to support endotoxin-induced host responses as a major contributing factor to the more than 25,000 deaths estimated to occur annually in the United States as a result of gram negative bacterial sepsis. Estimates of mortality in patients with profound shock due to endotoxin are 40-50 percent. Recent evidence has implicated cytokines released from endotoxin- stimulated lymphoreticular cells as major factors in the pathogenesis of endotoxin shock. The long range objective of this research project is to define the mechanism(s) by which LPS triggers the activation of lymphoreticular cells with specific focus on endotoxin receptors. For many of these studies, advantage will be taken of the mutant inbred C3H/HeJ mouse strain, whose lymphoreticular cells are refractory to stimulation with many LPS preparations. In this renewal application experiments are described to provide molecular, biochemical and immunologic characterization of a recently identified 80 kDa LPS-specific binding protein expressed on lymphoreticular cells of many species. We will investigate the hypothesis that this 80 kDA candidate LPS receptor serves an important biochemical function in cell activation. Monoclonal antibodies to this protein will be utilized to dissect specific LPS-receptor interactions, to follow the intracellular fate of the receptor and as affinity reagents to purify this molecule. Biochemical characterization and molecular cloning of the structural gene for this protein will be employed to understand further the function of this protein. Experiments to dissect the molecular basis for R-chemotype LPS activation of C3H/HeJ lymphoreticular cells will continue. It is suggested that the successful completion of these studies will contribute to our understanding of molecular interactions of LPS with host cells, and provide information of value in the design of therapeutically effective reagents to treat endotoxin shock.